Holiday days, public holidays, statutory leave and sickness are different systems. Do not assume that a red date on a calendar automatically gives every employee a paid day off.
Holiday entitlement
The statutory annual minimum is holiday hours equal to 4 times your weekly working hours. A 40-hour week therefore gives at least 160 statutory holiday hours per year. A CAO or contract may provide more.
Public holidays
The Netherlands has official public holidays, but there is no general law saying every employee must be off on each one. Check your CAO or employment contract for whether you are free, paid and/or receive an allowance for working.
Other leave
Statutory schemes include pregnancy/maternity leave, partner/birth leave, parental leave and forms of care leave. Other special leave—such as for a wedding or moving house—may come from your CAO or contract.
If you are sick
Follow your employer’s sickness-reporting procedure promptly. Dutch sickness/reintegration rules involve the employer, employee and occupational-health route; your normal huisarts is not simply the company doctor. Long-term sickness has specific wage-continuation and reintegration rules, so use UWV/Government guidance for the exact situation.